From c5ecf30aea4e89aeac142a077508c3e3b965d0c2 Mon Sep 17 00:00:00 2001
From: Albert Meltzer <7529386+kitbellew@users.noreply.github.com>
Date: Tue, 3 Sep 2024 09:52:59 -0700
Subject: [PATCH] Router: keep `then` NL cost at 1 even if no space

---
 .../main/scala/org/scalafmt/internal/Router.scala   |  6 +++---
 .../test/resources/scala3/OptionalBraces_keep.stat  | 13 ++++++-------
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
index d5f8ccf27b..81a195c542 100644
--- a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
+++ b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/Router.scala
@@ -2008,12 +2008,12 @@ class Router(formatOps: FormatOps) {
           Split(Newline, 1),
         )
       case FormatToken(_, _: T.KwThen | _: T.KwDo, _) =>
-        if (style.newlines.sourceIgnored || noBreak()) Seq(
-          Split(Space, 0)
+        val okSpace = style.newlines.sourceIgnored || noBreak()
+        Seq(
+          Split(!okSpace, 0)(Space)
             .withOptimalToken(nextNonCommentSameLineAfter(ft).left),
           Split(Newline, 1),
         )
-        else Seq(Split(Newline, 0))
       // Last else branch
       case FormatToken(_: T.KwElse, _, _) if (leftOwner match {
             case t: Term.If => t.elsep match {
diff --git a/scalafmt-tests/src/test/resources/scala3/OptionalBraces_keep.stat b/scalafmt-tests/src/test/resources/scala3/OptionalBraces_keep.stat
index 531741f585..c236d38a7e 100644
--- a/scalafmt-tests/src/test/resources/scala3/OptionalBraces_keep.stat
+++ b/scalafmt-tests/src/test/resources/scala3/OptionalBraces_keep.stat
@@ -106,13 +106,12 @@ object a:
      // c1
    }
 >>>
-Idempotency violated
-=> Diff (- obtained, + expected)
-    if reducePattern(caseBindingMap, scrutineeSym.termRef, cdef.pat)(using
--        gadtCtx
--      )
-+        gadtCtx)
-    then {
+object a:
+   if reducePattern(caseBindingMap, scrutineeSym.termRef, cdef.pat)(using
+        gadtCtx)
+   then {
+     // c1
+   }
 <<< if(cond) indentation
 trait A:
   val cond =